Today&rsquo;s Texas Republican Senate runoff between Lt. Gov. David Dewhurst and former state Solicitor General Ted Cruz is more than a mere primary. The winner, after all, is certain to win the seat of retiring Sen. Kay Bailey Hutchison (R) in November.

But even more, the result will say something about the state of the GOP, and it could have a long-term effect on the party, in the Senate and more broadly.

On virtually every major issue the Senate is likely to deal with during the next few years, Dewhurst and Cruz begin with the same goals and premises. But in terms of style, rhetoric, legislative philosophy and temperament, the two men are quite different.

Dewhurst, whose father was killed by a drunken driver when he was just 3, has plenty of ambition, and he has spent some of his considerable wealth during the past 15 years running first for land commissioner, then lieutenant governor and now Senator. His speaking style is very measured, and some of his supporters even describe him as &ldquo;polished&rdquo; and even &ldquo;aristocratic.&rdquo;

&ldquo;If Dewhurst and Cruz both said we should tear down Washington, D.C., David would say it in a very reasonable, soft-toned way while wearing an impeccably pressed shirt,&rdquo; one savvy political observer joked to me recently.

Dewhurst&rsquo;s style is one reason &ldquo;establishment Republicans&rdquo; are more comfortable with him than with Cruz, who seems unwilling to pass up even the smallest opportunity to bash the political establishment in Austin and Washington.

Cruz has the backing of the most confrontational conservative elements of his party, ranging from former Alaska Gov. Sarah Palin, RedState&rsquo;s Erick Erickson and media celebrity Sean Hannity to the Club for Growth, FreedomWorks, Rep. Ron Paul (R-Texas) and Sens. Jim DeMint (R-S.C.) and Mike Lee (R-Utah).

Cruz portrays the primary as an ideological battle, and he has referred to Dewhurst as a &ldquo;timid career politician&rdquo; who lacks the &ldquo;backbone to stand up and fight&rdquo; President Barack Obama and who has agreed to &ldquo;give away our liberties.&rdquo;

I interviewed Dewhurst in November of last year. While I certainly would not describe him as &ldquo;warm and fuzzy,&rdquo; he was thoughtful, serious and well-versed on matters of public policy. We discussed his background, record, views and campaign. He was relatively easy to interview, meaning he didn&rsquo;t duck and weave the way some candidates do.

I saw Cruz a couple of times in March of this year, and my interview with him couldn&rsquo;t have been more different from my experience with Dewhurst.

I normally begin interviews by getting some biographical information, to find out who the candidate is and what kind of personal narrative he might offer to voters. Only then do we move to the race and his campaign.

We did that with Cruz, but it was clear he didn&rsquo;t want to talk about his life story (which is interesting) as much as he wanted to prosecute his case. He went point by point as to why he was going to finish second in the initial primary vote and why he was going to win the runoff against the lieutenant governor.

I&rsquo;ve seen self-confident and aggressive candidates before, but Cruz, who has degrees from Princeton University and Harvard Law School and clerked for Chief Justice William Rehnquist, was off the charts on those two dimensions.

He seemed certain that he was right about everything and apparently believed it&rsquo;s unnecessary for a politician to connect with voters in any way other than on a checklist of issue positions. Given that style, he almost made Dewhurst seem warm and fuzzy.

There certainly is a big difference between the two Republican hopefuls, but I didn&rsquo;t see it as a matter of ideology. They both want lower taxes, less spending and less government, and they both support what conservatives refer to as traditional values.

The difference between the two men is simple: Cruz is not willing to compromise even if it means being irrelevant to the legislative process, while Dewhurst is willing to look for middle ground if that is what is needed to get things done.

To conservative activists such as Erickson, that difference defines Dewhurst as a moderate or liberal, even though conservative columnist George Will concluded that the assertion that Dewhurst is a moderate is &ldquo;nonsense.&rdquo;

Dewhurst, who has been endorsed by the third- and fourth-place finishers in the primary, former Dallas Mayor Tom Leppert and sportscaster Craig James, turns 67 in less than three weeks. Cruz turns 42 in December. The age difference is important because it suggests that Dewhurst is not likely to have a long-term effect on the state or national Republican Party, while Cruz could.

Indeed, given his worldview and personal style, I&rsquo;d expect Cruz to become a significant voice for conservative purists who believe their party has been too willing to give up on principle.

If elected, Cruz certainly will join the GOP&rsquo;s &ldquo;Uncompromising Caucus,&rdquo; which includes DeMint, Lee, Rand Paul (R-Ky.) and a handful of others, making it more difficult for his party&rsquo;s leadership and for the Senate to deal with the nation&rsquo;s problems.

If you like that idea, you&rsquo;ll like Cruz. If it scares the stuffing out of you, you&rsquo;ll prefer Dewhurst.